1. Field of the Invention
The invention relates to a series transmission system and, more particularly, to a series transmission system capable of working at different timings.
2. Description of the Prior Art
Today's electronic products, for example cell phones, PDA's, or personal computers, all comprise many micro-processing systems to organize multiple processing functions. In a micro-processing system, a method of sequential control of clock triggers is often utilized for making different devices perform different functions at different timings so that the whole micro-processing system can achieve predetermined functions. For example, if a micro-processing system has to achieve a certain function, the A circuit of the micro-processing system processes data first, and then the B circuit of the micro-processing system carries out the following process of the data. A micro-processing system can utilize the sequential control method to trigger the A circuit to start processing the data, and sequentially trigger the A circuit to transfer processed data to the B circuit. The micro-processing system then further triggers the B circuit to receive the processed data so that the B circuit can do the following processing operation on said data. In other words, through the above-mentioned triggering of the sequential control, the micro-processing system can coordinate the processing order of every circuit in the micro-processing system so that the micro-processing system can complete a certain function.
Before the micro-processing system transfers data to the transmission interface it often utilizes a byte as a unit. For saving transmission resources, however, the system sometimes divides the data into multiple bytes, transfers the data in these bytes, and transforms them back into the original data once they have been received. The above-mentioned transmission method, which utilizes bytes as units, is called the series transmission.
In the prior art, series transmission between each integrated circuit (IC) in the micro-processing system is accomplished through a specific transmission protocol (for example, I2C and SPI) according to the needed data form of the series transmission; or accomplished through a series transmission structure defined by an ASIC. This means that designers can define clock signals, series data signals, and series control signals of the series transmission, which saves the number of data transmission signals between ICs and accomplishes the purpose of data exchange between ICs. Generally speaking, the clock signals, the series data signals, and series control signals have different definitions and timings because the form and the application of series transmission can be different. Therefore, we often utilize two methods to design the series transmission interface. The first method is to design specific hardware to meet the demands of series transmission timing control according to the individual data form of each series transmission signal. The other method is to utilize one or more micro-controllers to meet these series transmission timing control demands.
Now, taking an inkjet printer as example, in order to achieve the goal of simple design and low cost the number of ICs can be reduced to 3 or 4. Please refer to FIG. 1, which is a block diagram of a printer 10 according to the prior art. As shown in FIG. 1, the printer 10 comprises a main control module for controlling and calculating image data, and controlling motors and memories; a memory module 14 used as an image data buffer, a program code buffer, and an inkjet state data buffer; a DC-DC converter and motor driver module 16 for supplying power and driving motors; and an inkjet driver module 18 for driving the inkjets. In the inkjet printer 10, modules having different functions utilize the following signals to communicate with each other and to process data. The first signal is the series transmission clock for triggering data signals. Generally speaking, there are three triggering methods; positive edge trigger, negative edge trigger, and both edges trigger. The second signal is the series transmission control signal. The control signal is often an enabling signal for controlling IC in a simple series transmission. Finally, the third signal is the series transmission data signal used as the register data of the IC to be controlled. Please note that the data signal can be unidirectional or bi-directional data.
Although modules transfer signals through the series transmission, IC modules from different producers may not utilize the same series transmission. In order to integrate all modules, the main control module 12 has to be designed as specific hardware to meet the demands of series transmission timing control according to the individual data form of each series transmission signal. The alternative option is for the main control module 12 to utilize one or more micro-controllers to meet the demands of series transmission timing control, again according to the individual data form of each series transmission signal. Therefore, if other modules (for example, the DC-DC converter and motor driver module or the inkjet driving module) change, the original series transmission signals are no longer used, causing the series transmission signals to have to be modulated. This causes a design problem.